US 8,619,542 B2 · Closed-loop feedback in wireless communications system

Abstract

A method and apparatus for providing channel feedback is provided herein. During operation a covariance matrix at time t (R) is calculated as a function of a received downlink signal. In order to reduce overhead, R is normalized and quantized. The base unit then uses the covariance matrix estimate to determine appropriate channel beamforming weights, and instructs transmit beamforming circuitry to use the appropriate weights. In an embodiment, circuitry performs a method of calculating a first precoding matrix index I from a codebook using a received signal, calculating a second codebook index J* using the first precoding matrix index I to approximate a covariance matrix and calculating a quantized coefficient α* to approximate the covariance matrix wherein the quantized coefficient α* is determined using the first precoding matrix index I.

Claims15

Dependent claims

A method comprising:

calculating a first precoding matrix index I from a codebook using a received signal;
calculating a second codebook index J* using the first precoding matrix index I to approximate a covariance matrix;
calculating a quantized coefficient α* to approximate the covariance matrix wherein the quantized coefficient α* is determined using the first precoding matrix index I, wherein J* and α* are determined as,
J
*
,
α
*
=
arg
⁢
⁢
min
J
∈
C
1
′
,
α
∈
C
0
⁢

R
tr
⁡
(
R
)
-
[
1
1
+
α
⁢
V
1
⁢
V
1
H
+
α
1
+
α
⁢
V
⁡
(
:
,
J
)
⁢
V
H
⁡
(
:
,
J
)
]

F
2
where α is a real scalar and takes any value contained in a scalar codebook C0,
V1 is a precoding vector from a rank-1 codebook C1,
V(:,J) denotes a vector (the Jth vector) from C1′,
R is the covariance matrix,
∥A∥F2 is the sum of the magnitudes of all entries of matrix A, and C1′ is a set of vectors and forms a rank-1 codebook, and
transmitting a codebook based covariance matrix using the first precoding matrix index I, the second codebook index J* and the quantized coefficient α*.

73 more elements

Dependencies are inferred from the claim text.

Closed-loop feedback in wireless communications system

Life of this patent

Closed-loop feedback in wireless communications system

Life of this patent

Abstract

Claims15